/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hdfs.server.namenode;

import java.util.Iterator;
import java.util.List;

import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.fs.permission.PermissionStatus;
import org.apache.hadoop.hdfs.protocol.QuotaExceededException;
import org.apache.hadoop.hdfs.server.blockmanagement.BlockStoragePolicySuite;
import org.apache.hadoop.hdfs.server.namenode.Quota.Counts;
import org.apache.hadoop.util.GSet;
import org.apache.hadoop.util.LightWeightGSet;

import com.google.common.base.Preconditions;

/**
 * Storing all the {@link INode}s and maintaining the mapping between INode ID
 * and INode.
 *
 * 存储所有的inode,并且维护了一份inode id和inode之间的映射关系
 *
 *
 */
public class INodeMap {

    static INodeMap newInstance(INodeDirectory rootDir) {
        // Compute the map capacity by allocating 1% of total memory
        int capacity = LightWeightGSet.computeCapacity(1, "INodeMap");
        GSet<INode, INodeWithAdditionalFields> map
                = new LightWeightGSet<INode, INodeWithAdditionalFields>(capacity);
        map.put(rootDir);
        return new INodeMap(map);
    }

    /** Synchronized by external lock. */
    private final GSet<INode, INodeWithAdditionalFields> map;

    public Iterator<INodeWithAdditionalFields> getMapIterator() {
        return map.iterator();
    }

    private INodeMap(GSet<INode, INodeWithAdditionalFields> map) {
        Preconditions.checkArgument(map != null);
        this.map = map;
    }

    /**
     * Add an {@link INode} into the {@link INode} map. Replace the old value if
     * necessary.
     * @param inode The {@link INode} to be added to the map.
     */
    public final void put(INode inode) {
        if (inode instanceof INodeWithAdditionalFields) {
            map.put((INodeWithAdditionalFields) inode);
        }
    }

    /**
     * Remove a {@link INode} from the map.
     * @param inode The {@link INode} to be removed.
     */
    public final void remove(INode inode) {
        map.remove(inode);
    }

    /**
     * @return The size of the map.
     */
    public int size() {
        return map.size();
    }

    /**
     * Get the {@link INode} with the given id from the map.
     * @param id ID of the {@link INode}.
     * @return The {@link INode} in the map with the given id. Return null if no
     *         such {@link INode} in the map.
     */
    public INode get(long id) {
        INode inode = new INodeWithAdditionalFields(id, null, new PermissionStatus(
                "", "", new FsPermission((short) 0)), 0, 0) {

            @Override
            void recordModification(int latestSnapshotId)
                    throws QuotaExceededException {
            }

            @Override
            public void destroyAndCollectBlocks(BlocksMapUpdateInfo collectedBlocks,
                                                List<INode> removedINodes) {
                // Nothing to do
            }

            @Override
            public Counts computeQuotaUsage(Counts counts, boolean useCache,
                                            int lastSnapshotId) {
                return null;
            }

            @Override
            public ContentSummaryComputationContext computeContentSummary(
                    ContentSummaryComputationContext summary) {
                return null;
            }

            @Override
            public Counts cleanSubtree(int snapshotId, int priorSnapshotId,
                                       BlocksMapUpdateInfo collectedBlocks, List<INode> removedINodes,
                                       boolean countDiffChange) throws QuotaExceededException {
                return null;
            }

            @Override
            public byte getStoragePolicyID() {
                return BlockStoragePolicySuite.ID_UNSPECIFIED;
            }

            @Override
            public byte getLocalStoragePolicyID() {
                return BlockStoragePolicySuite.ID_UNSPECIFIED;
            }
        };

        return map.get(inode);
    }

    /**
     * Clear the {@link #map}
     */
    public void clear() {
        map.clear();
    }
}
